Remington's "Practice of Pharmacy" states: "A good finished uncoated tablet will be firm enough to just break between the second and third fingers when using the thumb finger as a fulcrum." Attempts have been made to carry out such a test of a molded tablet hardness, but these have not given sufficiently reliable and reproduceable results to be depended upon. One vention as shown and described in connection with the drawings of this application, but the source of pressure fluid was led from the upper end of the machine over to a common communicating line between an upper pressure gauge and leading downwardly through a pressure cylinder to a plunger resting on the top of the tablet to be tested, which in turn rested on a fixed anvil below the tablet. This previous machine was not wholly reliable because of friction in the parts transmitting the fluid pressure downwardly to the top of the tablet and also because at times higher pressure was transmitted to the gauge than actually was necessary to break the tablet.
The present invention provides means for lightly holding a tablet to be tested vertically on edge between an upper and a lower member, together with means for transmitting a controlled fluid pressure to an air cylinder effective to raise the lower member upwardly to press against the tablet, together with a pressure-transmitting train above the tablet including a plunger in contact with the top of the tablet, a load cell in contact with that plunger, and pressure transmission means between the load cell and the pressure indicating gauge, all of this above the tablet being tested, together with means for adjusting the position of the parts to accommodate tablets of different diameter for testing, means for controlling the source of fluid pressure, etc., to obtain an efficient testing apparatus.
An object of the present invention is to provide method and means for testing the hardness of a molded tablet by holding the tablet vertically on edge with pressure transmitting members lightly clamping the tablet between them, and then means for transmitting a controlled fluid pressure against the tablet on one side, and transmitting the pressure coming through the tablet to a recording pressure gauge, whereby when the tablet breaks, no further transmission of pressure is possible and the gauge gives an accurate record of the maximum pressure used to disintegrate the tablet.
Other objects and advantages of this invention will be apparent from the drawings and description and the essential features thereof will be set forth in the appended claims.